The Effect of Lung Tumors Target Movement on Neutron Dose

Abstract

Abstract In radiation therapy, high energy photon above 10 MV could produce neutron. Small dose of neutron can provide biological effect in patient’s body in a long term with high risk. The study aims to recognize the distribution of neutron dose for the moving and non-moving target of tumor. Neutron dose was measured by using TLD 600(LiF: Mg,Ti) and TLD 100 (LiF: Mg.Ti) in tumor target and spinal cord as organs at risk (OAR). The study used In-House Dynamic Thorax phantom movable in translation and rotation within the amplitude of 5, 10, and 15 mm. Phantom was irradiated by the techniques of 3DCRT, IMRT, and VMAT using 15 MV. The result by calculation using thermal calibration factor shows that the average of distribution the neutron dose of tumor target was increase caused by the amplitude movements. On the technique 3DCRT, the dose of neutron increased by 9%, 34%, 68% respectively on the amplitude movements of 5, 10, and 15 mm, respectively, whereas increased by 2%, 25%, 70% respectively on the amplitude movements for IMRT techniques. Moreover, on the VMAT technique, it also increased by 3%, 8%, 54% respectively on the amplitude movements. The result of study shows that the distribution of neutron dose of tumor target and spinal cord increased with the amplitude increment and VMAT technique provided the highest dose of neutron compared to other techniques of irradiation.